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Avalanche Forecast

Archived

Feb 24th, 2021–Feb 25th, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

Another avalanche cycle may occur on Thursday, as snow and extreme wind are forecast. Travel in avalanche terrain is not recommended.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with snowfall, accumulation 15 to 25 cm, 100 km/h southwest wind, alpine temperature -6 C, freezing level rising to 500 m.

THURSDAY: Cloudy with snowfall, accumulation 10 to 20 cm, 80 km/h northwest wind, alpine temperature -5 C, freezing level 700 m.

FRIDAY: Cloudy with snowfall, accumulation 15 to 25 cm, 40 to 60 km/h northwest wind, alpine temperature -7 C.

SATURDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 40 to 60 km/h southwest wind, alpine temperature -5 C.

Avalanche Summary

More evidence of the avalanche cycle from earlier this week was observed as the skies cleared. For example, check out this MIN near Shames. This MIN shows excellent photos of slab avalanches around treeline elevations, potentially releasing on the surface hoar described in the Snowpack Summary.

Looking towards Thursday, another natural avalanche cycle may be triggered as a substantial amount of new snow and extreme wind are forecast. It will be a good day to stay well away from avalanche terrain!

Snowpack Summary

The region may see anywhere from 20 to 40 cm by Thursday afternoon above 800 m, with associated strong to extreme southwest to northwest wind. Storm slabs are expected to build rapidly in sheltered terrain and wind slabs in exposed terrain at high elevations. Below 800 m, rain will soak a snowpack that was recently wet. 

This snow will add to the 100 cm of snow that fell on the weekend, which may not be bonding well to previous surfaces buried mid-February, including:

  • Hard wind-affected snow, particularly in exposed alpine and treeline terrain,
  • Weak and feathery surface hoar in sheltered areas, with the most suspect elevation bands being lower alpine, treeline, and within openings below treeline,
  • A 20 to 40 cm thick layer of sugary faceted grains that developed during cold periods, and/or
  • A hard melt-freeze crust below treeline.

The mid-pack has been reported as being well-settled. There are presently no deeper concerns.

Terrain and Travel

  • Travel in alpine terrain is not recommended.
  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid the runout zones of avalanche paths. Avalanches could run full path.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.